Dynomaster - Need help with settings

[westwind77]

Figured I would have a little fun and make the upgrade from the 'butt dyno', so I installed the Dynomaster app on my Droid. 'Some people' say it actually can get pretty close, but you have to put in the correct info about your vehicle.

It is asking for the Weight (which I am sure I can look up easily), unless someone has down to the pound numbers from a weight station?

Curious is anyone knows how to calculate the Drivetrain Loss by %?

How about the 'Coefficient of Drag'?

Last, asks for the Frontal Area in Square feet. I can use a tape measure to get close to that one I guess.

This is all in fun just to see what it comes up with. I'm sure you could install this on 3 different phones and come up with 3 different results because of different hardware/software inside.

 

[1engineer]

I do not have any hard data on our 4Runner. What you need for this to be even close to accurate though is:
The weight has to be to the pound for your specific vehicle with you in it.
Drivetrain loss is different for every make and type of vehicle and is additive from engine back.
Cd is obtainable. I think the Toyota website has that data somewhere.
Frontal area is more complex than a tape measure can give. It is "effective" frontal area. So all angles need to determined and calculations need to be made. You cannot treat it as one big flat surface. Well, you can but it will cause your program to be worthless.
Unless you have the correct beginning numbers, your butt dyno will be much more accurate. Have fun!

 

[westwind77]

I do not have any hard data on our 4Runner. What you need for this to be even close to accurate though is:
The weight has to be to the pound for your specific vehicle with you in it.
Drivetrain loss is different for every make and type of vehicle and is additive from engine back.
Cd is obtainable. I think the Toyota website has that data somewhere.
Frontal area is more complex than a tape measure can give. It is "effective" frontal area. So all angles need to determined and calculations need to be made. You cannot treat it as one big flat surface. Well, you can but it will cause your program to be worthless.
Unless you have the correct beginning numbers, your butt dyno will be much more accurate. Have fun!

Ha, go figure, coming from an engineer! I know to get 100% output you need 100% input, but we all know that is not going to happen. I am curious what the output would looks like if I could get reasonably close input numbers.

Is there a formula to calculate drivetrain loss? If the front of the 4R was a piece of plywood the frontal area would be a breeze (no pun intended), but i know there are so many angles/grates/etc. Like I said though. I read in the reviews some people with SUV's & P/U's have gotten numbers to within single digits of the actual.

Now, all that being said even if you can get somewhat close (or not), and it is repeatable, with consistent numbers, and you make changes to the 4R you should be able to see changes good/bad, right?

 

[angrydog]

You could try these numbers, but I'm sure the drag coefficient wiuld differ from trail/SR5-Limited models due to hood scoop and small differences in the bumper.;

Drag Coefficient: .365cd
Curb Weight: 4805 Lbs
Drivetrain loss: ~.13%

I came up with the 13% by THIS POST. Gadget from URD stated that he got 205rwhp from a 4th Generation which estimated to be about 13% from its' crank of 236HP. I know the 5th Gen and the 4th Gen have similar drive trains so I still believe losses to be around ~13%. I can be totally wrong and Toyota engineers upped the anti and increased the drive train efficiency but I doubt they can beat laws of physics and pull much more efficiency out of crank.

So my guess of 5th Gen RWHP: 235RWHP

My findings are guesstimates, but I do have logic behind it and flamers; save it!

EDIT: Also Gadget's findings was from running in 2WD.

http://www.newcartestdrive.com/printversion-review.cfm?Vehicle=2010_Toyota_4Runner&ReviewID=4673

 

[1engineer]

For the fun of it use 80% efficiency and start from there. Let me edit this with a little note: Vehicle driveline efficiency changes with RPM. Always remember that. So, depending on which number you input up front (.75, .80, .83, etc) you could be right at some moment and totally wrong the next. It seems like you are just having fun with it so let us know!

 

[westwind77]

Cd is obtainable. I think the Toyota website has that data somewhere.

Ha, I'm getting there....

"The 2010 4Runner is lightly larger overall than the prior generation, but with the same wheelbase. Because the A-pillar has been moved forward slightly, the new 4Runner has a slightly more upright appearance. Still, the exterior is sleek enough to allow for a reduction in the coefficient of drag to 0.365 Cd."